With the development of wireless communications technologies, wireless performance of a terminal device becomes very important. Meanwhile, a miniaturization tendency of the terminal device further makes that an antenna, which is used to transmit and receive wireless signals, increasingly urgently needs to be converted from a traditional external form to a built-in form. However, due to an environment limitation, an existing form of built-in antenna is much poorer than an external antenna in terms of bandwidth, gain, and un-roundness of a pattern of a horizontal plane, which results in a decline in user satisfaction. Therefore, how to improve related performance specifications of a built-in antenna device becomes extremely urgent.
In the prior art, for most built-in antennas, a form of printing an antenna at an edge of a PCB (Printed Circuit Board, printed circuit board) is adopted. That is, an area is reserved at the edge of the PCB, and in this area, no component is placed, and there is also no wiring and ground, and an antenna is printed in this area, thereby achieving wireless communications. A separated printed antenna may also be adopted, and is electrically connected to the PCB, thereby achieving wireless communications. However, because the printed antenna and the PCB are on a same horizontal plane, for the antenna, there is a very small vertical polarization component and a large horizontal polarization component. However, in a case that wireless signals in a rural area are mainly vertically polarized, a bandwidth, a gain, and un-roundness of a pattern of a horizontal plane of the antenna are undesirable, which results in poor user experience.
Therefore, a built-in antenna is proposed in the prior art, and is implemented by adopting a manner of placing a monopole antenna or a PIFA (Planar Inverted-F Antenna, PIFA antenna) at an edge of a PCB and adding a passive parasitic unit at the same time. That is, a bright copper area which is grounded is added beside a feedpoint of the monopole antenna or the PIFA antenna, and a metal sheet or a FPC (Flexible Printed Circuit, flexible printed circuit) whose length is close to one quarter of a wavelength of a desired frequency band is connected to the bright copper area through a spring. In a manner of coupling resonance of the grounded metal sheet or the FPC, the bandwidth is broadened, so that it is achieved that the antenna works in several normal frequency bands adopted by GSM850 (GSM, Global System for Mobile communications, global system for mobile communications), GSM900, DCS (Distributed Control System, distributed control system), PCS (Personal Communications Service, personal communications service), UMTS2100 (UMTS, Universal Mobile Telecommunication System, universal mobile telecommunication system), and so on.
In the process of implementing the present invention, the inventor finds that the prior art has the following problems.
The bandwidth of the antenna can only meet specification requirements, the gain of the antenna is hard to be increased, and the un-roundness of the pattern of the horizontal plane is difficult to be improved. As a result, the user experience is still poor.